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M. W. DEWEY. ELECTRIC HEATING APPARATUS. No. 448,879. Patented Mar. 24,1891.

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WITNESSES:

UNITED STATES PATENT OFFICE.

MARK W. DElVEY, OF SYRACUSE, NEW YORK, ASSIGNOR TO THE DEWEYCORPORATION, OF SAME PLACE.

ELECTRIG=HEATENG APPARATUS.

SPECIFICATION forming part of Letters Patent No. 448,879, dated March24., 1891.

Application filed January 20, 1890. Serial No. 337,452. (No model.)

To aZZ 107mm it may concern.-

Be it known that I, llL-iRK XV. DEWEY, of Syracuse, in the county ofOnondaga, in the State of New York, have invented new andusefullmprovements in Electricdleating Apparatus, of which thefollowing, taken in connection with the accompanying drawings, is afull, clear, and exact description.

Myiuvention relates to electric-heating apparatus wherein theresistances or heat-develing electric conductors formed of platinum .orother metal are of comparatively small size, raised to a hightemperature by the passage therethrough of an electric current, andcovered, enveloped, or surrounded by a refractory material to preventthe temperature of the conductors being raised to a point sufficientlyhigh to melt and destroy them, and to serve to conduct the heattherefrom with sufficient rapidity to the case from which it isradiated.

The object of my invention is to pro vide a material with which tosurround or cover the resistances or wires that will not conductelectricity, will conduct the heat slowly, but with sufficient rapidityto prevent the burning of the wire, and to provide a material ofsufficient flexibility and elasticity to maintain the same in close andconstant contact with the conductor during all temperatures.

It is wellknown that a conductor varies in size in both itscross-section and length, according to the volume of current flowingthrough it, and in order to conduct the heat from the conductor in anyand all conditions I provide an elastic fibrous material that willmaintain perfect and constant contact with said conductor at all times,and that will make it impossible for the conductor to burn out by asudden rise of temperature.

Referring to the drawings, Figure 1 shows a plan of my electric heaterwith one heatdeveloping conductor enveloped or covered bya loose fibrousrefractory material. Fig. 2 shows a plan of a heater havingsevcralheatdeveloping conductors connected in parallel and surrounded bythe same refractory material. Fig. 3 is a side view of the heater withside of case removed, and showing ribs on top and bottom of case. Fig.shows side of case with cover removed to show elasticity of the loosefibrous refractory material within, the latter having raised of its ownaccord above the top edge of the metallic case upon the removal ofcover; and Fig. 5 is an end view of a heater with end removed to showthe resistance or heat-developing conductor in several layers, one abovethe other, with metallic plates between the layers to aid in conductingthe heat from the refractory packing material to the case of the heater.

Referring specifically to the drawings, Fig. 1 shows a resistance orheat-developing conductor A, formed of platinum, iron, or other suitablematerial, in a serpentine form and supported by pins or hooks Z), ofporcelain or other suitable material. The portions bent around the hooksare preferably of greater cross-section than the other portions of thewire to prevent excessive heating of the wire at these points. After thewire is suitably supported by the hooks Z), within the metallic case a,the wire is covered, enveloped, or surrounded with fibrous asbestus B orother fibrous refractory material. The bed for the conductors may beformed partly of a solid slab of refractory material, as fire-brick orplaster-of-paris; but this should not come in contact with the wires, asit is not yielding or elastic. c c are the terminals of the heater. Ifthe pins or hooks Z) are made of metallic material, they are insulatedfrom the case by strips of insulation (Z d.

The same letters of reference are used for the other figures.

In Fig. 2 the heat-developing conductors are connected in parallel tometallic strips cc on each side of the interior of the case and insulatcd therefrouiby strips of insulation (Z (Z.

The case a in Figs. 3, 4:, and 5 is preferably ribbed on the exterior toaid in radiating the heat therefrom, but may be corrugated or roughenedin any suitable manner for the same purpose.

Fig. 4: represents the cover removed from 9 the case a to show theelasticity of the fibrous packing material, it having raised slightlyabove the top edge of the case. The cover and screws employed forfastening it to the case serve as a binding device to maintain as it maybe made of earthenware.

close, constant, and continuous contact between thefibrousrefractorymaterialand the conductor or conductors.

Fig. 5 shows the resistance or heat-developing conductor A, arrangedinseveral planes or layers, with-loose metallic plates f between thelayers with their edgespreferablyin contact with the interior sidesofthe case a. The metallic plates fare separated and insulated from theconductor or conductors by the fibrous material which completelyenvelops said conductor or conductors. g are the feet of the heater,which raise it above'thefloorito increase the radiating-surface thereof.

I do not limit myself to the metallic case, The source oflectric'current'for the heaterunay be :a ibattery, dynamo, "or othersuitable source *well known, and not necessarytobeherein'shown'anddescribed.

Having described my invention, what'I able metallic case, one or moreresistances or heat-developing electric conductors within said case andformed in layers, metallic plates between the layers, a fibrousrefractory material in contact with and enveloping or covrugated orribbed metallic case, one ormore 1 resistances or heat-developingelectric con- -:ductorsisupported:in said case, and a fibrousv.refractorymaterial'envelopingor covering the conductors and incontinuous contact with the same. r

In testimony whereof I have hereunto signed my 'name, this l'8thdayof'January, 1890.

.MA-RK W. DEWEY. [L. s

tnesses:

'o. H. "DUELL,

C. L. *BEN'DLXON.

